Methods of making metal halide perovskites

ABSTRACT

Provided herein are methods of making metal halide perovskites, including methods of making bulk crystals or micro crystals. The metal halide perovskites may be a light emitting material.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 15/270,259, filed Sep. 20, 2016, which is incorporated hereinby reference.

Background

Hybrid organic-inorganic metal halide perovskites, which include a widerange of organic cations and inorganic anions, are a class ofcrystalline materials that can have structural tunability. By choosingappropriate organic and inorganic components, the crystallographicstructures can be controlled with the inorganic metal halide octahedronsforming various crystal structures surrounded by organic moieties (see,e.g., Mitzi, D. B. Journal of the Chemical Society-Dalton Transactions,1-12 (2001); Gonzalez-Carrero, S., et al. Part Syst Char 32, 709-720(2015); and Saparov, B. et al. Chem Rev 116, 4558-4596 (2016)). Theintegration of useful functionalities of both organic and inorganicportions within a single bulk assembly can enable these materials topossess unique electronic, magnetic, and optical properties. In recentyears, the use of hybrid organic-inorganic metal halide perovskites inoptoelectronic devices has been explored, including photovoltaic cells(PVs), light emitting diodes (LEDs), photodetectors, and opticallypumped lasers (see, e.g., Kojima, A., et al. J Am Chem Soc 131, 6050(2009); Tan, Z. K. et al. Nat Nanotechnol 9, 687-692 (2014); Ling, Y. C.et al. Adv Mater 28, 305-311 (2016); Dou, L. T. et al. Nat Commun 5(2014); Xing, G. C. et al. Nature Materials 13, 476-480 (2014); andStranks, S. D. et al. Nat Nanotechnol 10, 391-402 (2015).

The chemistry of metal halide perovskites can enable band gap controland color tuning. Highly luminescent 2D, quasi-2D, and 3D perovskiteshave been obtained with tunable, narrow emissions, by controllingchemical composition and quantum confinement (see, e.g., Protesescu, L.et al. Nano Lett 15, 3692-3696 (2015); Sichert, J. A. et al. Nano Lett15, 6521-6527 (2015); Dou, L. T. et al. Science 349, 1518-1521 (2015);and Yuan, Z. et al. Chem Commun 52, 3887-3890 (2016)). Broadbandemissions across the entire visible spectrum have also been realized incorrugated-2D and 1D perovskites (see, e.g., Dohner, E. R., et al. J AmChem Soc 136, 1718-1721 (2014); Dohner, E. R., et al. J Am Chem Soc 136,13154-13157 (2014); Hu, T. et al. J Phys Chem Lett 7, 2258-2263 (2016);Cortecchia, D. et al. arXiv 1603.01284 (2016)). Color tunability andhigh photoluminescence quantum efficiency (PLQE) can make metal halideperovskites desirable light-emitting materials. The research regardinghybrid organic-inorganic metal halide perovskites, however, has focusedon 3D and 2D structures instead of 1D and 0D structures (see, e.g.,Takeoka, Y., et al. Chem Lett 34, 602-603 (2005)).

Also, most high performance perovskites developed to date contain lead,which is a toxic heavy metal. Therefore, the use of lead can, in someinstances, present a challenge for the potential adoption of thesematerials because all lead-free metal halide perovskites discovered todate, such as tin and bismuth perovskites, have shown low PLQEs (see,e.g., Noel, N. K. et al. Energ Environ Sci 7, 3061-3068 (2014); Hao, F.,et al. Nat Photonics 8, 489-494 (2014); Park, B. W. et al. Adv Mater 27,6806 (2015); Jellicoe, T. C. et al. J Am Chem Soc 138, 2941-2944 (2016);and Peedikakkandy, L. et al. Rsc Advances 6, 19857-19860 (2016). Forexample, the 0D perovskite (CH₃NH₃)4PbI₆·2H₂O is non-emissive, and haslow stability under ambient conditions (Takeoka, Y., et al. Chem Lett34, 602-603 (2005)).

Therefore, perovskite materials having structures other than 1D, 2D or3D, and are stable, efficient, color tunable, lead free, and/or have arelatively high PLQE are desirable.

BRIEF SUMMARY

Provided herein are metal halide perovskites comprising a crystal havinga 0D structure, and a unit cell according to formula (I),R_(a)[MX₆]X_(d)   (I);wherein R is an organic ligand; a is 2 to 8; M is a metal atom; X is ahalide ion selected from Cl, Br, or I; MX₆ has an octahedral structure;and d is 2 to 10. In embodiments, the organic ligand is a C₁-C₂₀hydrocarbyl substituted with at least one of a protonated primary amine,a protonated secondary amine, or a protonated tertiary amine. The metalatom may be Sn, Cu, Ge, Mn, Co, Pb, Bi, or Eu.

Also provided herein are devices, including optoelectronic devices,comprising the metal halide perovskites of formula (I). The metal halideperovskites of formula (I) may be a light emitting material in thedevices, which can include a photovoltaic cell, a light emitting diode,a light emitting electrochemical cell, a photodetector, or an opticallypumped laser.

Also provided herein are methods of making a metal halide perovskiteaccording to formula (I). In one embodiment, the method comprisescontacting an organic ligand halide salt with a metal halide in a liquidto form a precursor liquid, and adding a precipitant to the precursorliquid to form one or more bulk single crystals of the metal halideperovskite. Microsize crystals of the metal halide perovskites offormula (I) also may be made by contacting an organic ligand halide saltwith a metal halide in a liquid to form a precursor liquid; and mixingthe precursor liquid with an organic liquid to form microsize crystalsof the metal halide perovskite.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1A depicts a crystal structure of one embodiment of a metal halideperovskite.

FIG. 1B depicts a single unit cell structure of the crystal of FIG. 1A.

FIG. 1C is a depiction of a space filling model of one embodiment of acrystal structure with a single octahedral MX₆.

FIG. 2 is a depiction of the powder X-ray diffraction patterns of oneembodiment of a metal halide perovskite in bulk crystal form and microcrystal form.

FIG. 3 is a plot of thermogravimetric analysis data collected for oneembodiment of a metal halide perovskite in bulk crystal form and microcrystal form, and for SnBr₂ and C₄N₂H₁₄Br₂.

FIG. 4A is a 2D AFM image of one embodiment of a microsize cystal.

FIG. 4B is a 3D AFM image of the microsize crystal of FIG. 4A.

FIG. 4C is a height profile of the 2D AFM image of FIG. 4A.

FIG. 5A is an SEM image of one embodiment of a micro size metal halideperovskite crystal.

FIG. 5B is an SEM image of one embodiment of a micro size metal halideperovskite crystal.

FIG. 5C is an SEM image of one embodiment of a micro size metal halideperovskite crystal.

FIG. 5D is an SEM image of one embodiment of a micro size metal halideperovskite crystal.

FIG. 6 includes images of bulk and microsize crystals of one embodimentof a metal halide perovskite under ambient light and UV light.

FIG. 7 depicts absorption and emission spectra of one embodiment of ametal halide perovskite in bulk crystal and micro crystal form.

FIG. 8 depicts the mechanism of exciton self-trapping of one embodimentof a metal halide perovskite.

FIG. 9 depicts the spectra for a PLQE measurement of one embodiment of ametal halide perovskite.

FIG. 10 depicts the emission decays at room temperature and 77 K of oneembodiment of a metal halide perovskite having a bulk crystal size andmicro crystal size.

FIG. 11 depicts the emission intensity versus excitation power for bulkand micro crystals of one embodiment of a metal halide perovskite.

FIG. 12 depicts the emission spectra (excited at 360 nm) at 77 K of bulkand micro crystals of one embodiment of a metal halide perovskite.

FIG. 13 depicts the photoluminescence stability of one embodiment of ametal halide perovskite under continuous illumination using a high powermercury lamp (150 mW/cm²).

FIG. 14 depicts the normalized excitation and emission spectra of acommercial blue phosphor and one embodiment of a metal halide perovskitethat is a yellow phosphor.

FIG. 15 includes images of different embodiments of blue and yellowphosphors, and their blends with different weight ratios.

FIG. 16 depicts emission spectra of one embodiment of a UV pumped lightemitting diode with different blending ratios of blue and yellowphosphors.

FIG. 17 depicts a chromaticity chart for one embodiment of a UV pumpedlight emitting diode with different blending ratios of blue and yellowphosphors.

FIG. 18 depicts emission spectra of one embodiment of a UV pumped whitelight emitting diode at different driving currents. FIG. 19 depictsemission spectra of one embodiment of a UV pumped white light emittingdiode operated in air for more than eight hours with a brightness ofabout 400 cd/m₂.

FIG. 20 depicts emission spectra of one embodiment of a 0D tin iodideperovskite.

DETAILED DESCRIPTION

Provided herein are metal halide perovskites having a 0D crystalstructure, including lead-free metal halide perovskites. The metalhalide perovskites are stable and/or have advantageous luminescentproperties, and the lead-free metal halide perovskites can beenvironmentally friendly. For example, the metal halide perovskiteshaving a 0D structure may exhibit Gaussian-shaped and strongly Stokesshifted yellow emission with PLQEs of 95±5%. The metal halideperovskites, including the lead-free metal halide perovskites, may bestable in air, including at ambient temperature and pressure. The metalhalide perovskites provided herein may have a bulk crystalline form or amicrosize crystalline form.

In embodiments, the metal halide perovskites provided herein have a 0Dstructure, and a unit cell according to formula (I):R_(a)[MX₆]X_(d)   (I);wherein R is an organic ligand; a is 2 to 8; M is a metal atom; X is ahalide ion selected from Cl, Br, or I; MX₆ has an octahedral structure;and d is 2 to 10. The metal atom may be Sn, Cu, Ge, Mn, Co, Pb, Bi, orEu. In one embodiment, R is an organic ligand, a is 3 to 5; M is Sn; Xis Br; MX₆ has an octahedral structure; and d is 3 to 5. In a furtherembodiment, R is an organic ligand, a is 4, M is Sn; X is Br; MX₆ has anoctahedral structure; and d is 4. In another embodiment, R is an organicligand, a is 3 to 5; M is Sn; X is I; MX₆ has an octahedral structure;and d is 3 to 5. In yet another embodiment, R is an organic ligand, a is4, M is Sn; X is I; MX₆ has an octahedral structure; and d is 4.Metal Atom

The metal atom of formula (I) may be capable of forming the octahedralstructure “MX₆”, wherein X is a halide ion selected from Cl, Br, or I.The metal atom, in embodiments, is selected from Sn, Cu, Ge, Mn, Co, Pb,Bi, or Eu.

Organic Ligand

The organic ligand of formula (I) generally may have any structure thatis compatible with the 0D crystal structure of the metal halideperovskites. For example, the organic ligand may include one or morepositively charged moieties, such as an amine. The positively chargedmoieties may interact favorably with the negatively charged halide ionsin the metal halide perovskites.

In one embodiment, the organic ligand is a C₁-C₂₀ hydrocarbyl or C₆-C₂₀aryl substituted with at least one positively charged moiety, such as apositively charged amine. In a certain embodiment, the organic ligand isa C₁-C₂₀ hydrocarbyl or C₆-C₂₀ aryl substituted with two to fourpositively charged moieties, such as two to four positively chargedamines. In a particular embodiment, the organic ligand is a C₁-C₂₀hydrocarbyl or C₆-C₂₀ aryl that is substituted with at least one of aprotonated primary amine, a protonated secondary amine, or a protonatedtertiary amine. In a further embodiment, the organic ligand is a C₁-C₂₀hydrocarbyl or C₆-C₂₀ aryl that is substituted with two to fourprotonated secondary amines. A protonated primary amine may have thefollowing structure: —NH₃ ⁺. A protonated secondary amine may have thefollowing structure: —NH₂R′⁺, wherein R′ is a C₁-C₂₀ hydrocarbyl. Aprotonated tertiary amine may have the following structure: —NHR″R′″⁺,wherein R″ and R′″ independently are a C₁-C₂₀ hydrocarbyl.

The phrase “C₁-C₂₀ hydrocarbyl,” as used herein, generally refers toaliphatic groups containing from 1 to 20 carbon atoms. Examples ofaliphatic groups, in each instance, include, but are not limited to, analkyl group, a cycloalkyl group, an alkenyl group, a cycloalkenyl group,an alkynyl group, an alkadienyl group, a cyclic group, and the like, andincludes all substituted, unsubstituted, branched, and linear analogs orderivatives thereof, in each instance having from 1 to about 20 carbonatoms. Examples of alkyl groups include, but are not limited to, methyl,ethyl, propyl, isopropyl, n-butyl, t-butyl, isobutyl, pentyl, hexyl,isohexyl, heptyl, 4,4-dimethylpentyl, octyl, 2,2,4-trimethylpentyl,nonyl, decyl, undecyl and dodecyl. Cycloalkyl moieties may be monocyclicor multicyclic, and examples include cyclopropyl, cyclobutyl,cyclopentyl, cyclohexyl, and adamantyl. Additional examples of alkylmoieties have linear, branched and/or cyclic portions (e.g.,1-ethyl-4-methyl-cyclohexyl). Representative alkenyl moieties includevinyl, allyl, 1-butenyl, 2-butenyl, isobutylenyl, 1-pentenyl,2-pentenyl, 3-methyl-1-butenyl, 2-methyl-2-butenyl,2,3-dimethyl-2-butenyl, 1-hexenyl, 2-hexenyl, 3-hexenyl, 1-heptenyl,2-heptenyl, 3-heptenyl, 1-octenyl, 2-octenyl, 3-octenyl, 1-nonenyl,2-nonenyl, 3-nonenyl, 1-decenyl, 2-decenyl and 3-decenyl. Representativealkynyl moieties include acetylenyl, propynyl, 1-butynyl, 2-butynyl,1-pentynyl, 2-pentynyl, 3-methyl-1-butynyl, 4-pentynyl, 1-hexynyl,2-hexynyl, 5-hexynyl, 1-heptynyl, 2-heptynyl, 6-heptynyl, 1-octynyl,2-octynyl, 7-octynyl, 1-nonynyl, 2-nonynyl, 8-nonynyl, 1-decynyl,2-decynyl and 9-decynyl.

The phrase “C₆-C₂₀ aryl,” as used herein, refers to aryl or aromaticmoieties that include from 6 to 20 carbon atoms. Examples of aryl oraromatic moieties include, but are not limited to, anthracenyl,azulenyl, biphenyl, fluorenyl, indan, indenyl, naphthyl, phenanthrenyl,phenyl, 1,2,3,4-tetrahydro-naphthalene, and the like, includingsubstituted derivatives thereof. Substituted derivatives of aromaticcompounds include, but are not limited to, tolyl, xylyl, mesityl, andthe like, including any heteroatom substituted derivative thereof.Examples of cyclic groups, in each instance, include, but are notlimited to, cycloparaffins, cycloolefins, cycloacetylenes, arenes suchas phenyl, bicyclic groups and the like, including substitutedderivatives thereof, in each instance having from about 3 to about 20carbon atoms. Thus heteroatom-substituted cyclic groups such as furanylare also included herein.

Unless otherwise indicated, the term “substituted,” when used todescribe a chemical structure or moiety, refers to a derivative of thatstructure or moiety wherein one or more of its hydrogen atoms issubstituted with a chemical moiety or functional group such as alcohol,alkoxy, alkanoyloxy, alkoxycarbonyl, alkenyl, alkyl (e.g., methyl,ethyl, propyl, t-butyl), alkynyl, alkylcarbonyloxy (—OC(O)alkyl), amide(—C(O)NH-alkyl- or -alkylNHC(O)alkyl), tertiary amine (such asalkylamino, arylamino, arylalkylamino), aryl, aryloxy, azo, carbamoyl(—NHC(O)O-alkyl- or —OC(O)NH-alkyl), carbamyl (e.g., CONH₂, as well asCONH-alkyl, CONH-aryl, and CONH-arylalkyl), carboxyl, carboxylic acid,cyano, ester, ether (e.g., methoxy, ethoxy), halo, haloalkyl (e.g.,—CCl₃, —CF₃, —C(CF₃)₃), heteroalkyl, isocyanate, isothiocyanate,nitrile, nitro, phosphodiester, sulfide, sulfonamido (e.g., SO₂NH₂),sulfone, sulfonyl (including alkylsulfonyl, arylsulfonyl andarylalkylsulfonyl), sulfoxide, thiol (e.g., sulfhydryl, thioether) orurea (—NHCONH-alkyl-).

In one embodiment of the metal halide perovskite of formula (I), theorganic ligand is a C₁-C₂₀ hydrocarbyl or C₆-C₂₀ aryl substituted withat least one positively charged moiety; a is 3 to 5; M is Sn, Cu, Ge,Mn, Co, Pb, Bi, or Eu; X is Br or I; MX₆ has an octahedral structure;and d is 3 to 5. In another embodiment, the organic ligand is a C₁-C₂₀hydrocarbyl or C₆-C₂₀ aryl substituted with at least one positivelycharged moiety, a is 4, M is Sn, Cu, Ge, Mn, Co, Pb, Bi, or Eu; X is Bror I; MX₆ has an octahedral structure; and d is 4. In a furtherembodiment, the organic ligand is a C₁-C₂₀ hydrocarbyl or C₆-C₂₀ arylsubstituted with at least one positively charged moiety, a is 4, M isSn; X is Br or I; MX₆ has an octahedral structure; and d is 4.

In one embodiment of the metal halide perovskite of formula (I), theorganic ligand is a C₁-C₂₀ hydrocarbyl or C₆-C₂₀ aryl substituted withtwo positively charged moieties; a is 3 to 5; M is Sn, Cu, Ge, Mn, Co,Pb, Bi, or Eu; X is Br or I; MX₆ has an octahedral structure; and d is 3to 5. In another embodiment, the organic ligand is a C₁-C₂₀ hydrocarbylor C₆-C₂₀ aryl substituted with two positively charged moieties, a is 4,M is Sn, Cu, Ge, Mn, Co, Pb, Bi, or Eu; X is Br or I; MX₆ has anoctahedral structure; and d is 4. In a further embodiment, the organicligand is a C₁-C₂₀ hydrocarbyl or C₆-C₂₀ aryl substituted with twopositively charged moieties, a is 4, M is Sn; X is Br or I; MX₆ has anoctahedral structure; and d is 4.

In one embodiment of the metal halide perovskite of formula (I), theorganic ligand is a C₁-C₂₀ hydrocarbyl or C₆-C₂₀ aryl substituted withat least one of a protonated primary amine, a protonated secondaryamine, or a protonated tertiary amine; a is 3 to 5; M is Sn, Cu, Ge, Mn,Co,

Pb, Bi, or Eu; X is Br or I; MX₆ has an octahedral structure; and d is 3to 5. In another, the organic ligand is a C₁-C₂₀ hydrocarbyl or C₆-C₂₀aryl substituted with at least one of a protonated primary amine, aprotonated secondary amine, or a protonated tertiary amine; a is 4, M isSn, Cu, Ge, Mn, Co, Pb, Bi, or Eu; X is Br or I; MX₆ has an octahedralstructure; and d is 4. In a further embodiment, the organic ligand is aC₁-C₂₀ hydrocarbyl or C₆-C₂₀ aryl substituted with at least one of aprotonated primary amine, a protonated secondary amine, or a protonatedtertiary amine; a is 4, M is Sn; X is Br or I; MX₆ has an octahedralstructure; and d is 4.

In one embodiment of the metal halide perovskite of formula (I), theorganic ligand is a C₁-C₂₀ hydrocarbyl or C₆-C₂₀ aryl substituted withtwo protonated secondary amines; a is 3 to 5; M is Sn, Cu, Ge, Mn, Co,Pb, Bi, or Eu; X is Br or I; MX₆ has an octahedral structure; and d is 3to 5. In another embodiment, the organic ligand is a C₁-C₂₀ hydrocarbylor C₆-C₂₀ aryl substituted with two protonated secondary amines; a is 4,M is Sn, Cu, Ge, Mn, Co, Pb, Bi, or Eu; X is Br or I; MX₆ has anoctahedral structure; and d is 4. In a further embodiment, the organicligand is a C₁-C₂₀ hydrocarbyl or C₆-C₂₀ aryl substituted with twoprotonated secondary amines; a is 4, M is Sn; X is Br or I; MX₆ has anoctahedral structure; and d is 4.

In one embodiment of the metal halide perovskite of formula (I), theorganic ligand is a C₁-C₂₀ hydrocarbyl or C₆-C₂₀ aryl substituted withthree protonated secondary amines; a is 3 to 5; M is Sn, Cu, Ge, Mn, Co,Pb, Bi, or Eu; X is Br or I; MX₆ has an octahedral structure; and d is 3to 5. In another embodiment, the organic ligand is a C₁-C₂₀ hydrocarbylor C₆-C₂₀ aryl substituted with three protonated secondary amines; a is4, M is Sn, Cu, Ge, Mn, Co, Pb, Bi, or Eu; X is Br or I; MX₆ has anoctahedral structure; and d is 4. In a further embodiment, the organicligand is a C₁-C₂₀ hydrocarbyl or C₆-C₂₀ aryl substituted with threeprotonated secondary amines; a is 4, M is Sn; X is Br or I; MX₆ has anoctahedral structure; and d is 4.

In one embodiment of the metal halide perovskite of formula (I), theorganic ligand is a C₁-C₂₀ hydrocarbyl or C₆-C₂₀ aryl substituted withfour protonated secondary amines; a is 3 to 5;

M is Sn, Cu, Ge, Mn, Co, Pb, Bi, or Eu; X is Br or I; MX₆ has anoctahedral structure; and d is 3 to 5. In another embodiment, theorganic ligand is a C₁-C₂₀ hydrocarbyl or C₆-C₂₀ aryl substituted withfour protonated secondary amines; a is 4, M is Sn, Cu, Ge, Mn, Co, Pb,Bi, or Eu; X is Br or I; MX₆ has an octahedral structure; and d is 4. Ina further embodiment, the organic ligand is a C₁-C₂₀ hydrocarbyl orC₆-C₂₀ aryl substituted with four protonated secondary amines; a is 4, Mis Sn; X is Br or I; MX₆ has an octahedral structure; and d is 4.

In one embodiment, the organic ligand is a compound according to thefollowing formula (A):

wherein each of R₁-R₆ is independently selected from hydrogen or amonovalent C₁-C₂₀ hydrocarbyl, and R₇ is a divalent C₁-C₂₀ hydrocarbylor C₆-C₂₀ aryl. In another embodiment, R₇ is a divalent, unsubstitutedC₁-C₂₀ hydrocarbyl, and the organic ligand is a compound according tothe following formula (B):

In a further embodiment, R₇ is a divalent, unsubstituted C₁-C₄hydrocarbyl, each of R₂, R₃, R₅, and R₆ is hydrogen, and the organicligand is a compound according to the following formula (C):

In a still further embodiment, R₇ is a divalent, unsubstituted C₁-C₄hydrocarbyl, each of R₂, R₃, R₅, and R₆ is hydrogen, each of R₁ and R₄is independently a monovalent, unsubstituted C₁-C₃ hydrocarbyl, and theorganic ligand is a compound according to the following formula (D):

In a particular embodiment, R₇ is a divalent, unsubstituted C₆ aryl, andthe organic ligand is a compound according to the following formula (E),which may be ortho-, meta-, or para-substituted:

In a further embodiment, R₇ is a divalent, unsubstituted C₆ aryl, eachof R₂, R₃, R₅, and R₆ are hydrogen, and the organic ligand is a compoundaccording to the following formula (F):

In a still further embodiment, R₇ is a divalent, unsubstituted C₆ aryl,each of R₂, R₃, R₅, and R₆ is hydrogen, each of R₁ and R₄ isindependently a monovalent, unsubstituted C₁-C₃ hydrocarbyl, and theorganic ligand is a compound according to the following formula (G):

In one embodiment, the organic ligand is a compound according to thefollowing formula (H):

wherein each of R₁ and R₃ is independently selected from a divalentC₁-C₂₀ hydrocarbyl, and each of R₂, R₄, and R₅ is independently selectedfrom hydrogen or a monovalent C₁-C₂₀ hydrocarbyl. In another embodiment,R₂ is hydrogen, R₄ and R₅ are independently monovalent, unsubstitutedC₁-C₃ hydrocarbyls, and R₁ and R₃ are independently divalent,unsubstituted C₂-C₄ hydrocarbyls, and the organic ligand is a compoundaccording to the following formula (I):

In a further embodiment, R₂ is a divalent, substituted C₂-C₄hydrocarbyl, wherein the substituent is a secondary amine, R₄ and R₅ areindependently monovalent, unsubstituted C₁-C₃ hydrocarbyls, and R₁ andR₃ are independently divalent, unsubstituted C₂-C₄ hydrocarbyls, and theorganic ligand is a compound according to the following formula (J):

In one embodiment, the organic ligand is a compound according to thefollowing formula (K):

wherein R₁ and R₅ are independently selected from a monovalent C₁-C₂₀hydrocarbyl or hydrogen, R₂ and R₄ are independently selected from adivalent C₁-C₂₀ hydrocarbyl, and R₃ is a divalent C₁-C₂₀ hydrocarbyl ora divalent C₆-C₂₀ aryl. In a particular embodiment, R₁ and R₅independently are unsubstituted, monovalent C₁-C₃ hydrocarbyls, R₂, R₃,and R₄ are independently unsubstituted, divalent C₂-C₄ hydrocarbyls, andthe organic ligand has a structure according to the following formula(L):

In one embodiment, the organic ligand is a compound according to thefollowing formula (M):

wherein n is 0 or 1, each of R₁-R₄ and R₈ is independently selected froma divalent C₁-C₂₀ hydrocarbyl, and each of R₅-R₇ is independentlyselected from a monovalent C₁-C₂₀ hydrocarbyl or hydrogen. In aparticular embodiment, n is 1, R₁-R₄ independently are unsubstituted,divalent C₁-C₄ hydrocarbyls, R₈ is an unsubstituted, divalent C₁-C₃hydrocarbyl, and R₅-R₇ independently are unsubstituted, monovalent C₁-C₃hydrocarbyls, and the organic ligand is a compound according to thefollowing formula (N):

In a further embodiment, n is 0, R₁-R₃ are unsubstituted, divalent C₁-C₄hydrocarbyls, and R₅-R₇ are unsubstituted, monovalent C₁-C₃hydrocarbyls, and the organic ligand is a compound according to thefollowing formula (O):

In one embodiment, the organic ligand is a compound according to thefollowing formula (P):

wherein m is 0 or 1, n is 1-4, each R₁ is independently selected from adivalent C₁-C₂₀ hydrocarbyl, and each R₂ is independently selected froma monovalent C₁-C₂₀ hydrocarbyl or hydrogen. In a particular embodiment,m is 0, n is 3, and R₂ is an unsubstituted, monovalent C₁-C₃hydrocarbyl, and the organic ligand is a compound according to thefollowing formula (Q):

In one embodiment of the metal halide perovskite of formula (I), theorganic ligand is selected from a compound of formula (A), (B), (C),(D), (E), (F), (G), (H), (I), (J), (K), (L), (M), (N), (O), (P), (Q), ora combination thereof; a is 3 to 5; M is Sn, Cu, Ge, Mn, Co, Pb, Bi, orEu; X is Br or I; MX₆ has an octahedral structure; and d is 3 to 5. Inanother embodiment, the organic ligand is selected from a compound offormula (A), (B), (C), (D), (E), (F), (G), (H), (I), (J), (K), (L), (M),(N), (O), (P), (Q), or a combination thereof; a is 4, M is Sn, Cu, Ge,Mn, Co, Pb, Bi, or Eu; X is Br or I; MX₆ has an octahedral structure;and d is 4. In a further embodiment, the organic ligand is selected froma compound of formula (A), (B), (C), (D), (E), (F), (G), (H), (I), (J),(K), (L), (M), (N), (O), (P), (Q), or a combination thereof; a is 4, Mis Sn; X is Br or I; MX₆ has an octahedral structure; and d is 4.

In one embodiment, the organic ligand is selected from a compoundaccording to structures (1)-(10):

In one embodiment of the metal halide perovskite of formula (I), theorganic ligand is selected from compound (1), (2), (3), (4), (5), (6),(7), (8), (9), (10), or a combination thereof; a is 3 to 5; M is Sn, Cu,Ge, Mn, Co, Pb, Bi, or Eu; X is Br or I; MX₆ has an octahedralstructure; and d is 3 to 5. In another embodiment, the organic ligand isselected from compound (1), (2), (3), (4), (5), (6), (7), (8), (9),(10), or a combination thereof; a is 4, M is Sn, Cu, Ge, Mn, Co, Pb, Bi,or Eu; X is Br or I; MX₆ has an octahedral structure; and d is 4. In afurther embodiment, the organic ligand is selected from compound (1),(2), (3), (4), (5), (6), (7), (8), (9), (10), or a combination thereof;a is 4, M is Sn; X is Br or I; MX₆ has an octahedral structure; and d is4.

In one embodiment, the organic ligand isN,N′-dimethylethane-1,2-diammonium, which has the following structure:

In one embodiment of the metal halide perovskite of formula (I), theorganic ligand is N,N′-dimethylethane-1,2-diammonium; a is 3 to 5; M isSn, Cu, Ge, Mn, Co, Pb, Bi, or Eu; X is Br or I; MX₆ has an octahedralstructure; and d is 3 to 5. In another embodiment, the organic ligand isN,N′-dimethylethane-1,2-diammonium; a is 4, M is Sn, Cu, Ge, Mn, Co, Pb,Bi, or Eu;

X is Br or I; MX₆ has an octahedral structure; and d is 4. In a furtherembodiment, the organic ligand is N,N′-dimethylethane-1,2-diammonium; ais 4, M is Sn; X is Br or I; MX₆ has an octahedral structure; d is 4;and the unit cell has the following formula: (C₄N₂H₁₄)₄[SnBr₆]Br₄.

Crystal Size

In embodiments, the metal halide perovskites provided herein are bulkcrystals. As used herein, the phrases “bulk crystals” or “bulkcrystalline form” generally refer to crystals having at least onedimension that is 500 μm or greater.

In embodiments, the metal halide perovskites provided herein are microcrystals. As used herein, the phrases “micro crystals” or “microsizecrystals” generally refer to crystals having an average largestdimension of about 15 μm to about 100 μm, as determined by scanningelectron microscopy (SEM). In one embodiment, the micro crystals have anaverage largest dimension of about 15 μm to about 50 μm. The microcrystals may be a powder.

OD Structure

In embodiments, the metal halide perovskites provided herein have a 0Dcrystal structure. The phrases “0D crystal structure” or “0D structure,”as used herein, refer to crystals having, within each unit cell, anoctahedral metal halide species that is separated from one or moreoctahedral metal halide species of adjacent unit cells by one or moreorganic ligands and/or one or more halide ions.

In one embodiment, the metal halide perovskite having a 0D structure isa tin bromide perovskite, as shown at FIG. IA, having unit cells of thefollowing formula: (C₄N₂H₁₄)₄SnBr₁₀. A unit cell of this formula isdepicted at FIG. 1B, which includes an individual tin bromide octahedron(SnBr₆ ⁴⁻) surrounded by C₄N₂H₁₄ ²⁺ and BP⁻ ions. Therefore, theforegoing formula may be rewritten as (C₄N₂H₁₄)₄[SnBr₆]Br₄. Similarly,FIG. 1C is a depiction of a space filling model of a core-shell quantumdot structure with SnBr₆ ⁴⁻ completely covered by C₄N₂H₁₄ ²⁺ and Br⁻ions. Therefore, as shown at FIG. 1B and FIG. 1C, the tin halideoctahedral SnBr₆ ⁴⁻ ions of this embodiment are completely isolated fromeach other and surrounded by C₄N₂H₁₄ ²⁺ and Br⁻ ions, which forms a bulkassembly of core-shell quantum dot like structures. Not wishing to bebound by any particular theory, it is believed that the strong quantumconfinement in such a 0D structure can result in efficient excitonself-trapping that produces broadband yellow emission.

In embodiments, the metal halide perovskites provided herein achievebroadband yellow light emission with near-unity quantum efficiency atroom temperature.

In one embodiment, the metal halide perovskite having a 0D structure isa tin iodide perovskite, having unit cells of the following formula:(C₄N₂H₁₄)4SnI₁₀.

In embodiments, the metal halide perovskites provided herein achievebroadband red light emission with near-unity quantum efficiency at roomtemperature.

In one embodiment, the metal halide perovskites provided herein have aPLQE of at least 90%. In another embodiment, the metal halideperovskites provided herein have a PLQE of at least 95%. In yet anotherembodiment, the metal halide perovskites provided herein have a PLQE ofat least 98%. In a still further embodiment, the metal halideperovskites provided herein have a PLQE of at least 99%.

Methods

Methods are provided herein for making metal halide perovskites. Themethods may be used to produce bulk and/or microsize crystals of themetal halide perovskites, which may have a 0D structure.

In embodiments, the methods comprise forming an organic ligand halidesalt by contacting an organic ligand precursor with an acid of theformula HX, wherein X is a halogen. The halogen may be Cl, Br, or I;therefore, the acid may be HCl, HBr, HI, or any combination thereof. Anyamount of acid may be used that is effective to form the organic ligandhalide salt. In one embodiment, about 1.5 to about 3.0 equivalents ofthe acid of the formula HX is used to form the organic ligand halidesalt. In another embodiment, about 2.0 to about 2.5 equivalents of theacid of the formula HX is used to form the organic ligand halide salt.In a still further embodiment, about 2.2 equivalents of the acid of theformula HX is used to form the organic ligand halide salt.

he organic ligand halide salt may be a halide salt of any of formulas(A)-(Q) or (1)-(10). In one embodiment, the organic ligand halide saltis N,N′-dimethylethane-1,2-diammonium bromide, and the organic ligandprecursor is N, N′-dimethylethylenediamine. In another embodiment, theorganic ligand halide salt is N,N′-dimethylethane-1,2-diammonium iodide,and the organic ligand precursor is N, N′-dimethylethylenediamine.

In embodiments, the methods provided herein comprise contacting anorganic ligand halide salt with a metal halide in a liquid to form aprecursor liquid; and adding a precipitant to the precursor solution toform one or more bulk single crystals of the metal halide perovskite.The metal halide and the organic ligand halide salt may be present inthe precursor liquid at a molar ratio of about 1:2 to about 1:6; about1:3 to about 1:5, or about 1:4. The liquid generally may be any liquidcapable of facilitating crystal formation, especially upon addition ofthe precipitant. In one embodiment, the liquid is a polar organicsolvent, such as dimethylformamide (DMF), dimethyl sulfoxide(DMSO),γ-butyrolactone (GBL). In a particular embodiment, the liquid isdimethylformamide (DMF). The precipitant may be any liquid capable offacilitating crystallization from the precursor liquid. In a particularembodiment, the precipitant is dichloromethane (DCM). Other liquids andprecipitants are envisioned. The precipitant may be added to theprecursor liquid at room temperature. The precipitant may be added overa period of about 5 to 12 hours. The bulk crystals may be produced at ayield of at least 50%, at least 60%, or at least 70%.

In embodiments, the methods provided herein comprise contacting anorganic ligand halide salt with a metal halide in a liquid to form aprecursor liquid; and mixing the precursor liquid with an organicliquid, such as toluene, to form micro crystals of the metal halideperovskite. The metal halide and the organic ligand halide salt may bepresent in the precursor liquid at a molar ratio of about 1:2 to about1:6; about 1:3 to about 1:5, or about 1:4. The liquid generally may beany liquid capable of facilitating crystal formation, especially uponaddition of the precursor liquid to the organic liquid. In oneembodiment, the liquid is a polar organic solvent, such asdimethylformamide (DMF). Stirring may be used to facilitate microcrystal formation upon, during, and/or after addition of the precursorliquid to the organic liquid. In a particular embodiment, the volumeratio of precursor liquid to organic liquid, upon complete addition ofthe precursor liquid to the organic liquid, is about 1:2 to about 1:6,from about 1:3 to about 1:5, or about 1:4. The precursor liquid and theorganic liquid may be combined in an inert atmosphere, such as in anitrogen glove box. The micro crystals may be produced at a yield of atleast about 50%, at least 60%, at least 70%, or at least 80%.

In embodiments, the metal halide used in the methods provided herein istin(II) bromide. In another embodiment, the metal halide used in themethods provided herein is bismuth(III) bromide. In a furtherembodiment, the metal halide used in the methods provided herein istin(II) iodide.

Devices

Provided herein are devices that include one or more metal halideperovskites. The metal halide perovskites provided herein, inembodiments, are light emitting materials in the devices. The metalhalide perovskites may emit light that is blue, green, yellow, orange,or red. Not wishing to be bound by any particular theory, it is believedthat the color emitted by the metal halide perovskites provided hereincan be changed or tuned by changing the metal atom, the halide ion, theorganic ligand, or a combination thereof.

In embodiments, the devices comprise at least two metal halideperovskites that emit light of different colors. For example, thedevices may include a first metal halide perovskite that emits bluelight, and a second metal halide perovskite that emits red light. As afurther example, the devices may include a first metal halide perovskitethat emits blue light, a second metal halide perovskite that emits redlight, and a third metal halide perovskite that emits green light. Incertain embodiments, the devices herein include full color displays. Thefull color display may be provided by two or more metal halideperovskites that emit light of different colors; or, alternatively, thefull color display may be provided by a combination of one or more metalhalide perovskites and one or more other materials, each of thematerials and one or more metal halide perovskites emitting differentcolors of light.

The devices include optoelectronic devices, such as a photovoltaic cell,a light emitting diode, a light emitting electrochemical cell, aphotodetector, and an optically pumped laser. In embodiments, thedevices provided herein are solid-state lighting devices.

In embodiments, a metal halide perovskite is a yellow phosphor in thedevices provided herein. The yellow phosphor may be mixed with one ormore other phosphors, which may be of different colors. For example, inone embodiment, the devices include one or more of the metal halideperovskites provided herein as a yellow phosphor, and the yellowphosphor is mixed with a blue phosphor. In a particular embodiment, theyellow phosphor is mixed with europium-doped barium magnesium aluminates(BaMgAl₁₀O₁₇:Eu²⁺), which is a commercial blue phosphor. In a furtherembodiment, the devices provided herein are white light emittingdevices.

In embodiments, the light emitting diodes comprise an anode, a cathode,and a light emitting layer. The light emitting diodes also may includeat least one of an electron transport layer and a hole transport layer.The anode may comprise indium tin oxide (ITO). The cathode may compriseLiF/Al. In particular embodiments, the light emitting diodes may furthercomprise at least one of a hole injection layer, an electron injectionlayer, a hole blocking layer, and an electron blocking layer. In oneembodiment, the light emitting layer comprises at least one of the metalhalide perovskites of formula (I).

EXAMPLES

The present invention is further illustrated by the following examples,which are not to be construed in any way as imposing limitations uponthe scope thereof. On the contrary, it is to be clearly understood thatresort may be had to various other aspects, embodiments, modifications,and equivalents thereof which, after reading the description herein, maysuggest themselves to one of ordinary skill in the art without departingfrom the spirit of the present invention or the scope of the appendedclaims. Thus, other aspects of this invention will be apparent to thoseskilled in the art from consideration of the specification and practiceof the invention disclosed herein.

The following materials were used in the Examples: tin (II) bromide,N,N′-dimethylethylenediamine (99%) (Sigma-Aldrich); hydrobromic acid (48wt. % in H₂O) (Sigma-Aldrich); dichloromethane (DCM, 99.9%) (VWR),dimethylformamide (DMF, 99.8%) (VWR), toluene (anhydrous, 99.8%) (VWR),and ethyl ether (VWR). All reagents and solvents were used withoutfurther purification unless otherwise stated.

Example 1 Solution Growth of (C₄N₂H₁₄)₄SnBr₁₀ Bulk Crystals

N,N′-dimethylethylene-1,2-diammonium bromide salts were prepared byadding hydrobromic acid solution (2.2 equiv, 48%) intoN,N′-dimethylethylenediamine (1 equiv) in ethanol at 0° C.

The organic salts were obtained after removal of the solvents andstarting reagents under vacuum, followed by washing with ethyl ether.The salts were dried and kept in a desiccator for future use.

Tin(II) bromide and N,N′-dimethylethylene-1,2-diammonium bromide weremixed at 1:4 molar ratio and dissolved in DMF to form a clear precursorsolution. Bulk single crystals were prepared by diffusing DCM into DMFsolution at room temperature for overnight. The large colorless crystalswere washed with acetone and dried under reduced pressure. The yield wascalculated at ˜70%.

Example 2 One Pot Synthesis of (C₄N₂H₁₄)₄SnBr₁₀ Microsize Crystals

Tin(II) bromide and N,N′-dimethylethylene-1,2-diammonium bromide weremixed at 1:4 molar ratio and dissolved in DMF to form a clear precursorsolution.

Microsize perovskite crystals were precipitated by adding 1 mL of thesolution to 5 mL toluene with vigorously stirring in a nitrogen filledglove box at room temperature.

The product was extracted from the crude solution via centrifugation andwashed with toluene, affording a white powder in a yield of ˜80% afterdried under vacuum.

Example 3 Single Crystal X-ray Diffraction (SCXRD)

The crystal structure of the bulk crystals was determined using singlecrystal X-Ray Diffraction (SCXRD). The SCXRD data is provided at Tables1-3 below. The data showed a OD structure with individual tin bromideoctahedral SnBr₆ ⁴⁻ ions completely isolated from each other andsurrounded by C₄N₂H₁₄ ²⁺ and Br⁻ ions, as depicted at FIG. 1A. It wasbelieved that this unique 0D structure was a bulk assembly of core-shellquantum dots (see Yoffe, A. D., Advances in Physics 50, 1-208 (2001)),in which the organic shells wrapped around the core Sn bromide dots, asshown at FIG. 1B.

TABLE 1 Single crystal x-ray diffraction data and collection parameters.The collection was performed at a temperature of 120 K. Compound(C₄N₂H₁₄)₄SnBr₁₀ Formula [(CH₃NH₂)₂C₂H₄]₄SnBr₁₀ Molecular weight 1278.40g/mol Space group P-1 (# 2) a 10.2070(4) Å b 10.6944(4) Å c 18.5996(6) Åα 94.043(3)° β 102.847(3)° γ 97.904(3)° V 1949.89(12) Å³ Z 2 ρ_(calc.)2.177 g/cm³ μ 10.922 mm⁻¹ Data collection range 2.815° < θ < 34.220°Reflections collected 57392 Independent reflections 11532 Parametersrefined 540 Restraints 240 R₁, wR₂ 0.0651^(a), 0.0511^(b)Goodness-of-fit on F² 0.9933 ^(a)R₁ = Σ ∥ F_(o) | − | F_(c) ∥/Σ | F_(o)∥. ^(b)wR₂ = [Σ w(F_(o) ² − F_(c) ²)²/Σ w(F_(o) ²)²]^(1/2)

TABLE 2 Atomic positions of (C₄N₂H₁₄)₄SnBr₁₀. All non-hydrogens wererefined with anisotropic displacement parameters, while the hydrogenswere refined with isotropic displacement parameters. All sites haveWyckoff position 2i. U_(eq), U_(iso) Atom x y z (Å²) Sn1 0.50513(4)0.73268(3) 0.25379(2) 0.0165(2) Br1 0.63291(5) 0.68065(5) 0.39545(3)0.0213(3) Br2 0.36628(5) 0.47903(5) 0.22695(3) 0.0201(2) Br3 0.71126(5)0.65033(5) 0.18028(3) 0.0189(2) Br4 0.28362(5) 0.82142(5) 0.32885(3)0.0209(3) Br5 0.65333(6) 1.02790(5) 0.28467(3) 0.0259(3) Br6 0.35651(6)0.77645(5) 0.08009(3) 0.0238(3) Br7 0.89569(6) 1.31403(5) 0.15163(3)0.0199(3) Br8 0.89768(6) 1.30727(5) 0.48454(3) 0.0208(3) Br9 −0.12538(6)0.79197(5) −0.02452(3) 0.0216(3) Br10 0.14702(6) 0.16762(5) 0.35492(3)0.0264(3) N1 −0.1487(4) 0.3684(4) 0.3152(2) 0.0185(2) N2 0.1579(4)0.4614(4) 0.4116(2) 0.0173(2) N3 0.8478(4) 1.0173(4) 0.0913(2) 0.0186(2)N4 1.1552(4) 1.1009(4) 0.1836(2) 0.0202(2) N5 0.4943(5) 1.0797(4)0.4118(2) 0.0258(3) N6 0.5755(4) 0.3819(4) 0.0600(2) 0.0193(2) N71.0250(4) 0.9133(4) 0.4135(2) 0.0201(2) N8 0.1107(4) 0.5285(4) 0.0968(2)0.0197(2) C9 −0.0652(5) 0.4954(5) 0.3320(3) 0.0182(3) C10 0.0849(5)0.4963(5) 0.3395(3) 0.0212(3) C11 0.3103(5) 0.4950(5) 0.4238(3)0.0230(3) C12 −0.2975(5) 0.3758(5) 0.3025(3) 0.0207(3) C13 0.9227(5)0.9734(5) 0.1602(3) 0.0203(3) C14 1.0719(6) 0.9736(5) 0.1650(3)0.0220(3) C15 1.3043(6) 1.0942(5) 0.1964(3) 0.0246(3) C16 0.6981(6)0.9905(5) 0.0830(3) 0.0268(3) C17 0.5067(6) 1.2206(6) 0.4308(3)0.0305(3) C18 0.5471(6) 1.0070(5) 0.4745(3) 0.0263(3) C19 0.4689(5)0.4533(5) 0.0221(3) 0.0207(3) C20 0.5201(6) 0.2788(5) 0.1004(3)0.0249(3) C21 0.9498(5) 0.9674(5) 0.4659(3) 0.0189(3) C22 0.9346(5)0.8435(5) 0.3441(3) 0.0206(3) C23 0.0734(5) 0.5268(5) 0.0151(3)0.0167(3) C24 0.0588(6) 0.6265(5) 0.1381(3) 0.0228(3) H11 −0.126(2)0.325(2) 0.3526(13) 0.028(2) H12 −0.133(2) 0.327(2) 0.2764(13) 0.027(2)H21 0.129(2) 0.498(3) 0.4479(12) 0.026(2) H22 0.139(2) 0.3787(19)0.4125(15) 0.026(2) H31 0.873(2) 1.0995(19) 0.0918(15) 0.029(2) H320.870(2) 0.980(3) 0.0524(12) 0.029(2) H41 1.131(2) 1.145(2) 0.1472(13)0.031(2) H42 1.138(2) 1.140(2) 0.2225(13) 0.031(2) H51 0.541(3) 1.068(2)0.3776(14) 0.039(2) H52 0.410(2) 1.046(2) 0.3915(16) 0.039(2) H610.642(2) 0.434(2) 0.0903(13) 0.028(2) H62 0.619(3) 0.350(2) 0.0275(13)0.028(2) H71 1.083(3) 0.976(2) 0.4017(14) 0.030(2) H72 1.075(3) 0.861(2)0.4371(12) 0.030(2) H81 0.200(2) 0.533(3) 0.1126(13) 0.029(2) H820.080(3) 0.452(2) 0.1078(13) 0.028(2) H91 −0.081(3) 0.532(3) 0.3771(13)0.022(2) H92 −0.097(2) 0.542(2) 0.2916(14) 0.022(2) H101 0.124(2)0.580(2) 0.3343(16) 0.025(2) H102 0.096(3) 0.435(3) 0.3013(13) 0.026(2)H111 0.357(3) 0.463(4) 0.4678(16) 0.036(2) H112 0.337(3) 0.587(2)0.429(2) 0.035(2) H113 0.337(3) 0.458(4) 0.3828(16) 0.035(2) H123−0.350(3) 0.293(2) 0.288(2) 0.031(2) H122 −0.318(3) 0.412(4) 0.3468(14)0.031(2) H121 −0.323(3) 0.427(3) 0.2635(17) 0.031(2) H131 0.913(3)1.029(3) 0.2012(12) 0.025(2) H132 0.883(2) 0.888(2) 0.1617(16) 0.025(2)H141 1.105(3) 0.924(2) 0.2044(14) 0.026(2) H142 1.087(3) 0.940(3)0.1188(13) 0.026(2) H151 1.355(3) 1.178(2) 0.211(2) 0.037(2) H1521.322(3) 1.058(4) 0.1514(14) 0.037(2) H153 1.328(3) 1.042(3) 0.2353(18)0.037(2) H163 0.651(3) 1.023(4) 0.0395(16) 0.039(2) H162 0.675(3)1.031(4) 0.1248(16) 0.039(2) H161 0.666(3) 0.900(2) 0.079(2) 0.039(2)H173 0.463(4) 1.257(3) 0.3877(14) 0.044(2) H172 0.601(2) 1.255(3)0.446(2) 0.045(2) H171 0.462(4) 1.237(3) 0.4705(19) 0.045(2) H1810.634(2) 1.052(3) 0.5003(13) 0.030(2) H182 0.560(3) 0.925(2) 0.4537(14)0.030(2) H191 0.436(3) 0.500(2) 0.0596(13) 0.025(2) H192 0.397(2)0.395(2) −0.0089(14) 0.025(2) H203 0.591(3) 0.234(3) 0.123(2) 0.035(2)H202 0.479(4) 0.313(3) 0.1381(18) 0.036(2) H201 0.453(3) 0.220(3)0.0662(14) 0.036(2) H211 0.901(3) 1.028(2) 0.4411(13) 0.024(2) H2120.892(3) 0.899(2) 0.4794(14) 0.024(2) H223 0.988(3) 0.804(3) 0.3149(16)0.029(2) H222 0.888(3) 0.903(2) 0.3172(16) 0.029(2) H221 0.868(3)0.782(3) 0.3574(15) 0.029(2) H231 0.089(3) 0.613(2) 0.0028(14) 0.020(2)H232 0.126(2) 0.475(3) −0.0067(13) 0.021(2) H243 0.108(3) 0.636(3)0.1880(12) 0.035(2) H242 0.073(4) 0.704(2) 0.1169(18) 0.035(2) H241−0.036(2) 0.600(3) 0.135(2) 0.035(2)

TABLE 3 Selected bonds and angles for (C₄N₂H₁₄)₄SnBr₁₀. Bond Distance(Å) Sn1—Br1 2.798 Sn1—Br2 2.838 Sn1—Br3 2.948 Sn1—Br4 3.125 Sn1—Br53.260 Sn1—Br6 3.345 Br1—Br8 4.795 Br1—Br10 4.747 Br2—Br7 4.741 Br2—Br94.583 Br2—Br10 4.817 Br3—Br7 4.336 Br3—Br9 4.746 Br4—Br8 4.494 Br4—Br104.166 Br5—Br7 4.828 Br5—Br8 4.607 Br5—Br10 4.905 Br6—Br7 4.464 Br6—Br94.901 Br7—Br9 3.897 Br8—Br10 4.217 Bonds Angle (°) Br1—Sn1—Br6 176.22Br2—Sn1—Br5 177.75 Br3—Sn1—Br4 178.91

The foregoing single crystal x-ray diffraction data of (C₄N₂H₁₄)₄SnBr₁₀was collected using an Oxford-Diffraction Xcalibur-2 CCD diffractometerwith graphite-monochromated Mo Kα radiation.

The crystal was mounted in a cryoloop under Paratone-N oil and cooled to120 K with an Oxford-Diffraction Cryojet. A complete sphere of data wascollected using ω scans with 1° frame widths to a resolution of 0.6 Å,equivalent to 2θ≈72.5°.

Reflections were recorded, indexed and corrected for absorption usingthe Oxford-Diffraction CrysAlisPro software, and subsequent structuredetermination and refinement was carried out using CRYSTALS, employingSuperflip to solve the crystal structure. The data did not allow for anunconstrained refinement: all hydrogens were restrained to theconnecting nitrogen or carbon.

The refinement was performed against F², with anisotropic thermaldisplacement parameters for all non-hydrogen atoms and with isotropicthermal displacement parameters for the hydrogens in the structure.Diamond was used as the crystal structure visualization software for theimages presented in the manuscript.

Example 4 Powder X-Ray Diffraction (PXRD)

The PXRD analysis was performed on Panalytical X'PERT Pro Powder X-RayDiffractometer using Copper X-ray tube (standard) radiation at a voltageof 40 kV and 40 mA, and X'Celerator RTMS detector. The diffractionpattern was scanned over the angular range of 5-50 degree (2θ) with astep size of 0.02, at room temperature. Simulated powder patterns werecalculated by Mercury software using the crystallographic informationfile (CIF) from single-crystal x-ray experiment.

The powder XRD (PXRD) patterns of ball-milled powders of bulk crystals(Example 1) and microsize crystals (Example 2) displayed almostidentical features, as shown at FIG. 2, which was believed to indicatethat both samples had the same crystal structure.

Example 5 Thermogravimetry Analysis (TGA), Atomic Force Microscopy(AFM), and Scanning Electron Microscopy (SEM)

Thermogravimetric Analysis (TGA)(FIG. 3), Atomic Force Microscopy(AFM)(FIG. 4A, FIG. 4B, and FIG. 4C), and Scanning Electron Microscopy(SEM)(FIG. 5) were also used to characterize the prepared samples, whichfurther confirmed that the bulk crystals prepared by solution growth andthe microsize crystals prepared by one-pot synthesis possess the samecompositions with only difference in crystal size.

TGA was carried out using a TA instruments Q50 TGA system. The sampleswere heated from room temperature (˜22° C.) to 800° C. with at a rate of5° C.·min⁻¹, under an argon flux of 40 mL·min⁻¹.

AFM measurements were conducted using Bruker Icon. All measurements wereperformed in the standard tapping mode in air with OTESPA tips fromBruker. FIG. 4A is a 2D AFM image of a microsize crystal (Example 2),and FIG. 4B is a 3D AFM image of the same crystal. FIG. 4C is a heightprofile of the 2D AFM image of FIG. 4A.

SEM images were taken using a FEI Nova NanoSEM 400. FIG. 5A, FIG. 5B,FIG. 5C, and FIG. 5D are SEM images of the 0D Sn bromide perovskite ofExample 2.

Example 6 Absorption Spectrum Measurements and Photoluminescence SteadyState Studies

Absorption spectra of both the bulk (Example 1) and microsize (Example2) perovskite crystals were measured at room temperature throughsynchronous scan in an integrating sphere incorporated into thespectrofluorometer (FLS980, Edinburgh Instruments) while maintaining a 1nm interval between the excitation and emission monochromators.

Steady-state photoluminescence spectra of both bulk (Example 1) andmicrosize (Example 2) crystals in solid state were obtained at roomtemperature and 77 K (liquid nitrogen was used to cool the samples) on aFLS980 spectrofluorometer.

The photophysical properties of the prepared bulk and microsize 0D Snbromide perovskite crystals were investigated using UV-Vis absorptionspectroscopy, as well as steady state and time-resolvedphotoluminescence spectroscopies. FIG. 6 depicts the images of the bulkand microsize crystals under ambient light and a hand-held UV lampirradiation (365 nm). Both the bulk and microsize crystals showed whitecolor under ambient light, and displayed strong yellow emission under UVirradiation.

FIG. 7 depicts the absorption and emission spectra of the bulk(Example 1) and microsize (Example 2) crystals.

A large apparent Stokes shift of >0.7 eV between the absorption andemission is observed, with the absorption edged at around 425 nm and theemission peaked at around 570 nm. The yellow emission also displayed alarge full width at half maximum (FWHM) of ˜105 nm (0.40 eV), which issimilar to that of the widely used cerium-doped yttrium aluminum garnet(Ce:YAG) yellow phosphor (see Tucureanu, V., et al. Opto-Electron Rev23, 239-251, (2015)).

The broadband yellow emission with large apparent Stokes shift wasbelieved to suggest that it was not from the direct free exciton excitedstates, but rather other excited states with lower energy. It is knownfor metal halides that the formation of self-trapped excited states canbe dependent on the dimensionality of the crystalline systems (see,e.g., Williams, R. T. et al. Journal of Physics and Chemistry of Solids51, 679-716 (1990); Shinozuka, Y. et al. Journal of the Physical Societyof Japan 64, 3007-3017(1995); Georgiev, M., et al. Pure Appl Chem 67,447-456 (1995); Ishida, K. Z Phys B Con Mat 102, 483-491(1997); and Wu,X. X. et al. J Am Chem Soc 137, 2089-2096 (2015)).

It was believed that 0D structured systems with the strongest quantumconfinement would be most favorable for the formation of self-trappedexcited states, because, at least in part, there was no potential energybarrier separating the free exciton and self-trapped excited states. Theyellow emission from the 0D Sn bromide perovskites was very similar tothe 2.2 eV emission from SnBr₂ crystals at low temperature, which wasbelieved to be attributed to the radiative decay of self-trappedexcitons (see Yamasaki, Y. et al. International Journal of ModernPhysics B 15, 4009-4012 (2001)).

Therefore, the excited state processes for the 0D Sn bromide perovskitesof the foregoing examples could be depicted in the configurationcoordinate diagram shown at FIG. 8. FIG. 8 depicts the mechanism ofexciton self-trapping, including a configuration coordinate diagram forthe self-trapped excitons in 0D Sn bromide perovskites (the straight andcurved arrows represent optical and relaxation situations,respectively). Upon photon absorption, the perovskites were excited tothe high energy free exciton excited states, which were believed toundergo ultrafast relaxation to the lower energy multiple self-trappedexcited states to generate broadband photoluminescence. This behaviorappeared to be very similar to that of heavy metal phosphorescentmaterials, because the molecules were believed to be photo-excited tothe singlet states, which underwent ultrafast intersystem crossing toform the lower energy triplet states that caused phosphorescentemission. Unlike corrugated 2D and 1D perovskites emitting from bothfree exciton and self-trapped excited states at room temperature due tothermally activated equilibrium, the 0D perovskites of the foregoingexamples were believed to emit from the self-trapped excited statesonly, further confirming that 0D structures most favor excitonself-trapping.

Example 7 Photoluminescence Quantum Efficiencies (PLQEs)

The PLQEs of bulk (Example 1) and microsize (Example 2) crystals weremeasured to be near-unity (95±5%), as shown at FIG. 9, which wasbelieved to be the highest value yet achieved for any metal halideperovskite. FIG. 9 shows the excitation line of reference and emissionspectrum of the metal halide perovskite of Example 1 collected by anintegrated sphere.

For photoluminescence quantum efficiency measurement, the samples wereexcited using light output from a housed 450 W Xe lamp passed through asingle grating (1800 l/mm, 250 nm blaze) Czerny-Turner monochromator andfinally a 5 nm bandwidth slit.

Emission from the sample was passed through a single grating (1800 l/mm,500 nm blaze) Czerny-Turner monochromator (5 nm bandwidth) and detectedby a Peltier-cooled Hamamatsu R₉₂₈ photomultiplier tube. The absolutequantum efficiencies were acquired using an integrating sphereincorporated into the FLS980 spectrofluorometer.

The PLQE was calculated by the equation: η_(QE)=I_(S)/(E_(R)-E_(S)), inwhich I_(S) represents the luminescence emission spectrum of the sample,E_(R) is the spectrum of the excitation light from the empty integratedsphere (without the sample), and E_(S) is the excitation spectrum forexciting the sample.

Control samples, rhodamine 101 and blue phosphor BaMgAl₁₀O₁₇:Eu²⁺, weremeasured using this method to give PLQEs of ˜98% and ˜93%, which areclose to the literature reported values. The PLQEs were double confirmedby a Hamamatsu C₉₉₂₀ system equipped with a xenon lamp, calibratedintegrating sphere and model C₁₀₀₂₇ photonic multi-channel analyzer(PMA).

Example 8 Time-Resolved Photoluminescence

FIG. 10 depicts the decay curves of yellow emissions from the bulk andmicrosize crystals at room temperature, giving almost identicallifetimes of ˜2.2 μs.

Time-Resolved Emission data were collected at room temperature and 77 K(liquid nitrogen was used to cool the samples) using time-correlatedsingle photon counting on a Horiba JY Fluoromax-4 Fluorometer. Sampleswere excited with 295 nm pulsed diode lasers. Emission counts weremonitored at 530 nm. The average lifetime was obtained bymultiexponential fitting.

Example 9 PL Intensity Dependence on Excitation Power Density

To verify the origin of the yellow emission from the intrinsicself-trapped excited states, the dependence of emission intensity onexcitation power for bulk (Example 1) and microsize (Example 2) crystalsat room temperature was measured, as well as their emissions at 77 K. Asshown in FIG. 11, the intensity of the broadband emission exhibits alinear dependence on the excitation power up to 500 W/cm², which wasbelieved to suggest that the emission did not arise from permanentdefects (see Dohner, E. R., et al. J Am Chem Soc 136, 13154-13157(2014)).

FIG. 12 shows the emission spectra of bulk and microsize crystals at 77K, which have a much smaller FWHM of 62 nm, as compared to 105 nm atroom temperature. This narrowing was consistent with the theoretical andexperimental results obtained for lead halide perovskites with excitonself-trapping, where there are multiple self-trapped excited states andvibrational bands giving different emission energies at roomtemperature, but fewer favorable ones with less vibrational transactionsat low temperature.

The emission peaks blue shift at 77 K (from 570 to 530 nm) with thelifetimes (˜2.0 μs) slightly shorter than those at room temperature,which was believed to suggest that the excitons may concentrate more onthe lower energy excited states with larger band gap and faster decayrate, i.e. the first downward pointing arrow in FIG. 8.

PL intensity versus power studies were carried out on an EdinburghInstruments PL980-KS transient absorption spectrometer using a ContinuumNd:YAG laser (Surelite EX) pumping a Continuum Optical ParametricOscillator (Horizon II OPO) to provide 360 nm 5 ns pulses at 1 Hz. Thepump beam profile was carefully defined by using collimated laser pulsespassed through an iris set to 5 mm diameter. Pulse intensity wasmonitored by a power meter (Ophir PE10BF-C) detecting the reflectionfrom a beam splitter. The power meter and neutral density filters werecalibrated using an identical power meter placed at the sample position.Neutral density filters and an external power attenuator were used toreduce the pump's power density to the desired power range. Detectionconsisted of an Andor intensified CCD (1024×256 element) cameracollecting a spectrum from 287 nm to 868 nm and gated to optimize PLcollection (typically a 30 to 50 ns gate depending on PL lifetimestarting immediately following the 5 ns laser pulse). 100 collectionswere averaged at each power level with every laser pulse monitored todetermine the average intensity. PL intensity was determined at themaximum of the PL emission curve.

Example 10 Materials Photostability Study

To test the photostability, a 100 W 20 V mercury short arc lamp was usedas continuous irradiation light source. The intensity of the irradiationwas calibrated to 150 mW/cm². The photoluminescence was measured atperiodic intervals on a HORIBA iHR₃₂₀ spectrofluorimeter, equipped witha HORIBA Synapse CCD detection system.

The Sn based materials of the foregoing examples showed greatphotostability under continuous high power mercury lamp irradiation (150mW/cm²), with more stable emission recorded in nitrogen environment thanin air (FIG. 13).

Example 11 UV Pumped LEDs

To demonstrate the potential application of the foregoing 0D Sn bromideperovskites as yellow phosphor, optically pumped white LEDs werefabricated by blending the microsize crystals (Example 2) withcommercial blue phosphors (BaMgAl₁₀O₁₇:Eu²⁺) in a polydimethylsiloxane(PDMS) matrix.

Considering the excitations of both the yellow and blue phosphors in theUV region (see FIG. 14), a commercial UV LED (340 nm) was used as thelight source. FIG. 15 depicts the images of blue phosphors, yellowphosphors, and their blends with different weight rations (1:2, 1:1, and2:1) embedded in PDMS under ambient light and a hand-held UV lampirradiation.

The emission spectra of UV pumped LEDs, in which phosphors doped PDMSfilms were attached to the commercial UV LED, are shown at FIG. 16. TheCIE color coordinates and Correlated Color Temperatures (CCTs) are shownat FIG. 17.

A range of “warm” to “cold” white lights was achieved by controlling theblending ratio between the two phosphors. With a blue/yellow weightratio of 1:1, a white emission with CIE coordinates of (0.32, 0.35), aCCT of 6260 K, and a color-rendering index (CRI) of 75, was obtained.

Excellent color stability was observed in this white LED at differentoperating currents, as shown at FIG. 18. It was believed that this wasdue to the little-to-no energy transfer from the blue phosphors to theyellow phosphors, as there was a minimum overlap between the excitationof yellow phosphors and the emission of blue phosphors (FIG. 14). Thewhite LED also showed great device stability in air with almost nochange of light brightness and color during the preliminary testing,i.e., the device continuously on at ˜400 cd/m² for more than eight hoursunder the same operating power (FIG. 19).

The blue (BaMgAl₁₀O₁₇:Eu²⁺) and yellow ((C₄N₂H₁₄)₄SnBr₁₀) phosphors wereblended with Sylgard 184 polydimethylsiloxane (PDMS) encapsulant, andput in a polytetrafluoroethylene (PTFE) mold to control shape andthickness.

The whole mold was heated at 100° C. for 40 min in an oven to cure PDMS.The phosphors doped PDMS films were then attached to a UVTOP® UV LEDwith window, 340 nm, 0.33 mW (THORLABS) to form UV pumped LEDs. The LEDswere driven by a Keithly 2400 sourcemeter and emission spectra wererecorded on an Ocean Optics USB4000 Miniature Fiber Optic Spectrometer.For device stability test, a white light LED was continuously powered bya Keithley 2400 at a stable current power to give a brightness of ˜400cd/m². Emission spectra were recorded at periodic intervals using anOcean Optics USB4000 Miniature Fiber Optic Spectrometer.

Example 12 0D Tin Iodide Perovskites

Using the procedures of Examples 1 and 2, a series of 0D tin iodideperovskites were made. The 0D tin iodide perovskites of this example hadthe following structure:(C₄N₂H₁₄)₄[SnI₆]I₄

FIG. 20 shows the emission spectra of the sample of bulk crystals ofthis example at room temperature (R.T.) and 77 K. The bulk crystals ofthis example had a largest dimension of about 1 mm, and a thickness ofabout 0.5 mm. The emission data indicated that the crystals of thisexample released red light (from 620 to 650 nm), which demonstrated thataltering the halide ion was used successfully to tune or change thecolor of light emitted by the 0D perovskites of Examples 1 and 2, andthose of the current example.

While the present invention may be embodied in many different forms,disclosed herein are specific illustrative embodiments thereof thatexemplify the principles of the invention. It should be emphasized thatthe present invention is not limited to the specific embodimentsillustrated.

We claim:
 1. A method of making a metal halide perovskite, the methodcomprising: contacting an organic ligand halide salt with a metal halidein a liquid to form a precursor liquid, wherein the metal halide is tin(II) bromide or tin (II) iodide; and adding a precipitant to theprecursor liquid to form one or more bulk single crystals of the metalhalide perovskite, wherein the bulk single crystals have a 0D structure.2. The method of claim 1, further comprising contacting an organicligand precursor with an acid of the formula HX, wherein X is a halogen,to form the organic ligand halide salt.
 3. The method of claim 2,wherein the acid is HBr, the organic ligand precursor isN,N-dimethylethylenediamine, and the organic ligand halide salt is N,N′-dimethylethane-1,2-diammonium bromide.
 4. The method of claim 1,wherein the metal halide and the organic ligand halide salt are presentin the precursor liquid at a molar ratio of about 1:2 to about 1:6. 5.The method of claim 1, wherein the metal halide and the organic ligandhalide salt are present in the precursor liquid at a molar ratio ofabout 1:3 to about 1:5.
 6. The method of claim 1, wherein the liquidcomprises a polar organic solvent.
 7. The method of claim 6, wherein thepolar organic solvent comprises dimethylformamide (DMF), dimethylsulfoxide (DMSO),γ-butyrolactone (GBL), or a combination thereof.
 8. Themethod of claim 1, wherein the precipitant comprises dichloromethane(DCM).
 9. The method of claim 1, wherein the bulk crystals are formed ata yield of at least 50%.